The present invention relates to lubrication of an anti-friction bearing and particularly to a feed bushing which is adapted to receive a supply of lubricant or grease and is disposed axially between two rows of anti-friction bearing ball elements and radially between a bearing bushing and a shaft inside that bearing bushing. The invention has particular application to double row anti-friction bearings with two axially spaced rows of balls.
To assure dependable operation of anti-friction bearings, various greases and oils are used for their lubrication. For single-row bearings, lifetime lubrication is frequently employed, especially when the bearing is covered on both sides. For readily accessible bearings, relubrication from the outside, via or grease nipples, or the like, is effected at certain intervals.
In double-row bearings in which the shaft at the same time forms the inner bearing ring and in which the external bearing bushing forms the outer ring or in which there are installed outer rings, suitable relubrication or lifetime lubrication is possible only at great expense, and, because of the small amount of space required, such lubrication is done only with complicted devices.
Certain bearing lubricating devices are known which use grease supply bushings. For instance, German Utility Model DE-Gbm No. 19 26 519 mentions a porous intermediate bushing (of sintered material, or the like). Before that bushing is installed, it is impregnated with the base oil or the grease used. The impregnation is done in a vacuum. Such bushings are used predominantly as plain bushings with emergency operating properties. Another disadvantage is that, as a result of the stream of air caused by the rotating shaft, particles of oil detach themselves from the sintered bushing, and the entire bearing space is wetted. There is no possibility of directed lubrication.
In German Provisional Patent DE-AS No. 23 34 186, a supplementary lubricating device is proposed which, with compact construction, forms a storage space. The additional lubricating results from centrifugal force only upon the rotation of the complete bearing package. In addition to the high expense of this device, high speeds of rotation cannot be reached with rotating outer rings due to the large masses in rotation. The lubricating device can, therefore, be used only in connection with particularly slow running devices.
In German Utility Model DE-Gbm No. 72 38 730, an additional lubricating chamber is described which is intended predominantly for idling wheels of rail vehicles. In this case, as already described in German Provisional Patent No. 23 34 186, the outer ring of the bearing rotates. In addition to the high expense which such a chamber causes, it is also not possible in this case to provide directed additional lubrication of the bearing. Holes are introduced axially into the closure covers and radially into the surrounding bushing and are intended to permit the emergence of the oil. They extend over the entire space surrounding the bearing. The holes must be filled before any drop of oil reaches the bearing.
Furthermore, previously known feed bushings for ball bearings in which the races are arranged directly in the shaft or in the external bearing bushing make the introduction of the rolling element balls into the races difficult. This is because there is a small amount of space between the shaft and the bearing bushing within which the feed bushing is also arranged. As a result, extensive deflection of the shaft is not possible for installing the balls.